Remote switch status sensor



w 1386- 1 s. H. FRASE 3,545,476

REMOTE SWITCH STATUS SENSOR Filed May 1, 1989 UTlL. DEVICE PULSE "F/g. SOURCE Fig. 2

INVENTOR SYLVA/V H. FRASE BY/WMZ ATTORNEY United States Patent O M 3,546,476 REMOTE SWITCH STATUS SENSOR US. Cl. 30788 Claims ABSTRACT OF THE DISCLOSURE A circuit for determining the status, i.e., whether opened or closed, of a remotely located switch; the switch may be representative of an ON, OFF electronic circuit such as a bistable multivibrator or a set of contacts on an electro-mechanical relay. The switch status initially establishes the magnetic state of a core of low residual magnetism in a low or, alternatively, in a high steadystate of magnetic flux density. A second signal source inductively coupled to the core induces a large or, alternatively, a small flux change in the core due to its low or high steady-state magnetic fiux density, which flux change is detected by an inductively coupled utilization device as being indicative of the status of the switch.

BACKGROUND OF THE INVENTION The present invention relates to a means for ascertaining the status, whether opened or closed, of a remotely located switch which switch may represent any type of opened, closed electrical device. The environment in which the present invention is located is an electronic data processing system having a plurality of remotely located control units coupled to a single central processor. The

central processor samples certain interconnecting wires between it and the control units and responds approprinately to the condition of each of the interconnecting wires.

In the prior art configuration, the switch was comprised of a set of contacts in a press-to-set switch on the control panel of the remotely located control units. The pressing of the switch coupled an appropriate signal to the interconnecting wires which signal set a flip-flop stage of a register in the central processor. The central processor sampled the register and responded appropriately. In such configuration an electromechanical relay was used in place of the core of the present'invention with relay contact bounce and cost, space requirements being eliminated, or reduced, by the use of the present invention.

SUMMARY OF THE INVENTION The present invention relates to a circuit for setting the magnetic state of a core of low residual magnetization into a steady state of relatively low or, alternatively, relatively high flux density as being indicative of the status of an associated switch being opened or closed.

With the switch closed, a control signal is inductively coupled to the core through a serial circuit of a voltage source, a current limiting resistor, a diode, a control winding about the core and a Zener diode. Coupled in parallel circuit across the diode, the winding and the Zener diode is a capacitor for absorbing transient signals that are induced in the control winding while the Zener diode and the diode are conducting. The forward biased diode passes the control signal through the control winding and onto the Zener diode; the Zener diode is operated in its reversed biased condition providing a relatively constant voltage drop thereacross for a relatively wide range of reverse current changes therethrough. The control signal flowing through the control winding maintains the mag- 3,546,476 Patented Dec. 8, 1970 ICC netic state of the core at a substantially stable state of relatively high flux density. The subsequent inductive coupling of a strobe pulse to the core induces a relatively small output signal in an inductively coupled output winding which relatively small output signal is detected by the associated utilization device as being indicative of the switch being closed.

With the switch opened, no control signal is inductively coupled to the core so that it remains in its magnetic state of low residual magnetization. The subsequent inductive coupling of a strobe pulse to the core induces a relatively large output signal in the output winding, which relatively large output signal is detected by the utilization device as being indicative of the switch being opened. 1

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an illustration of the preferred embodiment of the present invention.

FIG. 2 is an illustration of the hysteresis loop characteristic of the core of FIG. 1 in its operating conditions thereon.

DESCRIPTION OF THE PREFERRED EMBODIMENT With particular reference to FIG. 1 there' is presented an illustration of the preferred embodiment of the present invention in which the status, opened or, alternatively, closed, of switch 10 established the magnetic state of core 12 of low residual magnetization in a relatively low or, alternatively in a relatively high steady state of magnetic flux density. Pulse source 14, through pulse winding 15, couples a pulse signal to core 12 thereby inducing a large or, alternatively, a small flux change in core 12 due to its low or high steady state of magnetic flux density. The flux change in core 12 is detected by utilization device 16, through output winding 17, as being indicative of the status of switch 10.

With particular reference to FIG. 2 there is presented an illustration of the hysteresis loop 20 characteristic of core 12 of FIG. 1. With no magnetomotive force coupled to core 12 the magnetic state of core 12 is along its B axis as in point 22. Point 22 may be considered to be the first initial magnetic stable state of core 12. Subsequently, with the coupling of a positive magnetomotive force, +Ni to core 12 its magnetic state goes along loop 20 as through points 24, 26, 28 as a function of the intensity of the applied magnetomotive force. This wellknown characteristic is utilized in the present invention to provide a relatively low or a relatively high output signal indicative of the status of switch 10 being opened or closed causing the magnetic state of core 12 to reside at point 22 or point 26.

With switch 10 opened, voltage source 30 is caused to couple no current signal to control winding 32 which winding is coupled in series circuit with resistor 34, diode 36, Zener diode 38 and switch 10. Accordingly, the magnetic state of core 12 is that of point 22 of FIG. 2. The subsequent inductive coupling of a strobe pulse to core 12 by pulse source 14, through its winding 15, generates a magnetomotive force N i (N being the number of turns of winding 15 about core 12, i being the current signal flowing through winding 15 due to pulse source 14) in core 12 causing the magnetic state of core 12 to move along its hysteresis loop 20 from its first initial magnetic state represented by point 22 to a second magnetic state represented by point 24. This substantial change in flux density, AB in core 12 induces in winding 17 a substantial voltage causing the current signal i to be coupled to utilization device 16. Utilization device 16 interprets this relatively large output signal as being indicative of switch 10 being opened, i.e., the magnetic state of core 12 was at an initial state represented by 44, N =12 turns #38 enameled, wound on opposite, point 22. second, half of core 12.

The magnetomotive force of N2i2 in core 12 is also It is apparent that applicant has disclosed herein an seas?at:ss iziiasatguziatis3:23:11: i of a F ocate switc control winding 32 is isolated from the remainder of the What I Claim is:

control signal circuit and is not absorbed thereby. Tlns 1. A circuit for determining the Status of a Switch,

isolation through Zener diode 38 is achieved by selecting comprising:

a Zener diode having a breakdown voltage greater than a core of 10 W re Si dual magnetism;

the maXiInuIn amplitude of the Voltage sighal induced l first, second and third windings inductively coupled to in control winding 32 due to the magnetomotive force of said core;

N i in core 12. This isolation of control winding 32 awn/[1.01 Signal Source; from the remainder of the control circuit with switch a limiting resistor;

opened permits a maximum current signal i to be a diode;

coupled to utilization device 16. a Zener i d With switch 10 closed, voltage source 30 is coupled a Switch; in series circuit with limiting resistor 34, diode 36, winda capacitor; ihg 32, Zener diode 38 and Switch The i slgnal said control signal source, said limiting resistor, said from voltage source 30 passes through resistor 34 and diode Said first Winding Said Zener diode and i forward biases diode 36. Zener diode 38 is then reversed Switch coupled in Series circuit; biased, and it is caused to Operate in the range that F said capacitor coupled in parallel circuit with said vides a nearly constant voltage drop thereacross wlde diode, Said first winding and Said Zener diode; range of negative current therethrough. Resistor 34 limits 3 pulse source coupled across Said Second winding; and the magnthlde of chrreht Signal i1 in the senes ch'cult a utilization device coupled across said third winding. ensuring a substantially constant steady state value for The circuit of claim 1 wherein with Said Switch 1 1 Which is the magnetomotive folCe coupled he closed, said control signal is coupled to said first winding 12 Causing its magnetic State to assume a Second lmhal for establishing the magnetization of said core in a submagnet Stable State represented by POiht 26 on 10013 20 stantially saturated magnetic stable-state along its hystereof FIG. 2. sis loop.

The subsequent inductive coupling of the strobe pulse 3- The circuit of claim 2 wherein Said pulse Source to core 1 by Pulse Sollree 14 in its assoclated Wlhdmg couples a pulse signal to said second winding for causing 15 generates a magnetomotive force of N i in core 12 an insubstantial fl change in Said com Causing the magnetic State of Core 12 to move along his 4. The circuit of claim 3 wherein said utilization device hysteresis lo p 20 from its Second initial maghehc Stable detects, through said third winding, said insubstantial flux state represented by point 26 to a second magnetic state change in Said core as Said switch being opened represented by Poiht This insubstantial change in flux 5. The circuit of claim 1 wherein with said switch density, 2 in core induces in Winding 17 a rela' opened, said control signal is not coupled to said first tiVely Small Output Signal which relatively Small p t winding for establishing the magnetization of said core Signal is detected y utilization device 16 as being lhdlca' in its low residual magnetic stable-state along its hysteretive of switch 10 being closed, i.e., core 12 was initially Sis 16 at a magnetic State represented by P 26 0h hysteresls 6. The circuit of claim 5 wherein said pulse source loop 20 of FIG. 2. couples a pulse signal to said second winding for causing The magnetomotive force of N i in core 12 is also asubstantial fl change i Said core, coupled to Control Winding However, With diode 36 7. The circuit of claim 6 wherein said utilization de and Zener diOde 38 Conducting, the induced Signal in vice detects, through said third winding, said substantial i101 Winding 32 is coupled to capacitor 49 which flux change in said core as said switch being opened. stantially absorbs the induced signal. Thus, With switch 8. A circuit for determining the status of a witch, 10 closed, i.e., with diode 36 and Zener diode 38 coni i dueling, the flux change in core 12 due to the coupling a core of low residual magnetism coupled in series of the strobe pulse thereto is substantially absorbed by 50 i i capacitor 40 rather than reflected into output Winding 17 a control i l Source; and, accordingly, utilization devic 1 a limiting resistor;

In order to facilitate an understanding of the operation a di d of this invention, the following group of actual values afir t i di i d ti l l d to id core; for the components of the illustrated embodiment are aZener di d presented. It should be understood that the principles of a it h h i an opened or a l d Status; operation of this circuit may be present in circuits having a capacitor coupled in parallel circuit with said diode, a wide range of individual specifications, so that the list said first winding and said Zener diode. of values here presented should not be construed as a 9. The circuit of claim 8 including means coupled to limitation thereto. said core for determining the magnetic stable-state of said core along its hysteresis loop as a function of the status Core 12 Supermalloy Tape-Wound Bobbin ID. .095, of id it h,

OD. .225, Ht. .175 10. The circuit of claim 9 wherein said diode and said Zener dlode 38 IN753A 6.2 volt Zener diode are coupled oppositely poled to opposite ends Diode 36 IN4086 of said first winding. Capacitor 40 0.01 ,uf. 100 v. ceramic Resistor 34 watt 1800 ohms References Cited Windings: UNITED STATES PATENTS 32, N =1l0 turns #40 enameled, confined t0 filSt 2 937 2 5 5 19 0 Olsen 307 g half of Core 2,998,531 8/1961 Kiyasu et a1. 307-88 42, N =12 turns #38 enameled, wound on top of N STANLEY M. URYNOWICZ, JR., Primary Examiner 

